The present invention relates to a power amplifier, and, more particularly, to a power amplifier that is substantially phase stable while operating over a region of substantially constant (limited) output power.
In certain applications, such as, for example, supplying RF energy to a plurality of transmitting sections of a phased-array radar antenna, it is desirable to maintain the power level to each section within predetermined power and phase limits in order to assure proper side-lobe reduction and beam-steering accuracy, respectively, over the desired RF frequency operating range. For example, in a phased-array radar system, a transmission path may include class C power amplifier stages. Such path may typically exhibit amplitude modulation (AM) to phase modulation (PM) conversion factor, or drive phase pushing, on the order of 20.degree./dB, which places severe demands on drive power level tolerance, or prohibits achieving close tolerances on transmission path phase accuracy.
It would be desirable to provide an amplifier able to maintain a constant output power level, such as for example 10 watts, and a constant transmission phase within small tolerances over a useful range of input power. In addition, it would be desirable to provide a simple scheme for establishing a good impedance match to the input port of the amplifier from a source and appropriate load matching, and especially complex output port matching, for efficient amplifier operation. By "useful range of input power" is meant that the amplifier is able to accommodate a range of input power that is beneficial to the user or operator of the amplifier in the selected application of the amplifier at the desired frequencies of operation.
Accordingly, it is an object of the present invention to provide an amplifier able to maintain a constant output power level and a constant transmission phase within small tolerances over a useful range of input power.
Another object of the present invention is to provide a simple scheme for establishing source and load impedance matching and especially complex output port matching, of an amplifier to a source and load impedance, respectively, for efficient amplifier operation.